Vehicle restraints have been employed to prevent accidental movement of a truck away from a loading dock during a loading operation. When the truck is parked in front of the loading dock, the rear end of the truck completely encloses the doorway in the loading dock with the result that the truck driver cannot observe the loading or unloading of cargo from the truck by a lift truck or other mechanical handling equipment. To prevent the truck from accidentally pulling away from the dock before the loading or unloading operation is completed, vehicle restraints have been used which are mounted on the loading dock and engage the ICC bar located at the rear end of the truck.
Certain types of vehicle retraints employ a pivoting hook that is pivoted either manually or through mechanical means from the storage position to the locking position where it will engage the ICC bar.
Other vehicle restraints, such as disclosed in U.S. Pat. No. 4,488,325 employ a linear moving hook which is moved vertically along the front face of the dock from a lower storage position to an upper locking position. In the vehicle restraint, as described in the aforementioned patent, an electric motor is mounted on the hook and operates through a gear transmission to rotate a pinion which is engaged with a rack mounted on the loading dock. With this construction, operation of the pinion and rack mechanism will drive the hook upwardly and downwardly between the lower inoperative position and the upper operative position where the hook is engaged with the ICC bar.
During a loading operation, the truck bed may rise and fall relative to the dock as a fork lift truck moves between the dock and the truck bed. The truck bed will also rise relative to the dock as cargo is unloaded from the truck bed, and conversely, the truck bed will fall relative to the dock as cargo is loaded onto the truck bed and the truck springs are compressed. It is important that a vehicle restraint have the capability of maintaining the hook in engagement with the ICC bar as the truck bed floats relative to the dock. In certain instances, depending upon the type of truck, the float can be up to ten inches.